Adsorbent materials and use thereof

ABSTRACT

A method for absorbing hydrophobic substances in liquid form, by subjecting the liquid to contact with an adsorbent material comprising fibers in knop form, which has a spherical fiber orientation gained in the knopping process. The knopping process parameters form the fibers into knops of a wide range of densities in order to allow optimized oil adsorbency for a range of oil viscosities. The fibrous material can be modified by including the use of chemicals, such as water repellants, to modify the surface characteristics of the fibers to enhance oil pick-up or flotation. The fibrous material can be used in conjunction with a containment device made of netting or porous material shaped into an elongated system or pad to allow oil and oil water mixtures to penetrate the netting.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to material for use in adsorbing spillages ofliquid organic substances.

2. The Prior Art

A major pollution problem is the spillage of large amounts of oil suchas when being transported in bulk on the sea or on land, The damagecaused by such spillages is well documented. There have been numerousattempts at providing methods and materials to overcome this problem.Suggestions have been materials to adsorb the spilled oil, substancesdesigned to enable the oil to mix with water and physical barriersdesigned to inhibit the spread of oil for example when a spillage occursat sea. One material that is available commercially is that marketed bythe 3M Company of the USA under the trade mark "POWERSORB" or "OILSORB".This may consist of layers of fibrous polypropylene encased in suitablenetting and shaped as long elongate systems designed to float on thesurface of water and act as a physical barrier to the spread of the oilas well as being designed to adsorb the oil. The adsorbencycharacteristics of the polypropylene has been on of the attributes totheir successful use. While oil spillages are the most well recognisedproblem, spillages of other large quantities, of generally liquidorganic materials can also be environmentally serious. The materialsinclude large amounts of vegetable oils, refined oils and such like.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a material having goodadsorbency for oil and other organic materials.

In accordance with this invention there is provided a method foradsorbing hydrophobic substances in liquid form, comprising subjectingthe liquid to contact with an adsorbent material comprising fibresformed into entangled bodies call knops.

"Knops" are small balls of entangled fibres, i.e., fibres which arewrapped and/or felted on themselves, and are essentially spherical inshape.

Knops can be manufactured by machinery of the general type described inU.S. Pat. No. 4,761,857 for the manufacture of longtailed neps, and itis possible to increase the versatility of application of the fibers toadsorb organic or synthetic oils by this means. The material can be usedin any loose, uncontained form.

The loose fibrous material in knop form has its additional containmentattributes gained by having a spherical fibre orientation.

The fibrous material in knop form has increased buoyancy attributes in awater medium compared to that of fibrous material not in knopped form.

Variations in the process for making knops can cause the knops to have awide range of densities in order to allow optimised oil adsorbency for arange of oil viscosities.

The fibrous material can be modified by including the use of chemicals,such as water repellents, to modify the surface characteristics of thefibres and enhance the oil pick-up or bouyancy of the material in water.

The fibrous material can be used in conjunction with a containmentdevice made of netting or porous material shaped into an elongatedsystem or pad to allow oil and oil water mixes to penetrate the netting.

The fibrous material can be used in conjunction with other fibres orbuoyancy aids to increase the oil adsorbancy or knop buoyancy in water.

The fibrous material can be used in conjunction with bacterial nutrientssuch as Inipol 22 to allow bacteria to break down the oil.

The fibrous material can be used as a filter to filter oil from and oiland water mixture.

The fibrous material can be used in with reused, dyed or undyed fibrousmaterials in knop form.

The fibrous material is preferably knops of wool. Knops have a number ofuses primarily as a fill such as in upholstery, pillows and otherhousehold articles, but their very high adsorbancy character for organicliquids, particularly oil, more particularly crude oil, has never beensuggested before.

It has been known that wool has an affinity for oil, particularly ifsome of the natural wool grease remains on the fibre. After forming toknops this affinity increases greatly. It is thought this increase inaffinity is created by the spherical shape of the fibres comprising theknop. The oil tends to break up into droplets and then migrate into thecentre of each knop. It is this ability which can be exploited by usingthe knops as a means of adsorbing oil spills. A few simple laboratorytest revealed that untreated knops could adsorb up to thirty times theirown weight of viscous oils.

Laboratory tests in a water bath indicate that wool knops will adsorboil more readily if allowed to float unconstrained on the surface of theoil-water interface. If contained in a netting their adsorbtion rate isslower, but they should maintain their original adsorbency rate providedthey are not packed or loaded too tightly.

The invention envisages using other fibres of natural or syntheticpolymers which can be formed into entangled bodies of fibre of the typeenvisaged by the invention.

The invention also envisages using mixtures of various types ofsynthetic or naturally occurring fibres in the form of discreteentangled bodies.

Woollen knops have demonstrated in trials to be of particular value asan adsorbent material and have the further advantage in that virtuallyany type and grade of wool can be used to make the knops. Thus, evenshort staple fibres can be used together with either scoured orsemi-scoured wool, crutchings and other waste remnants or other fibrousby-products.

The size of the entangled bodies of fibre is not currently envisaged asbeing critical. It is also envisaged that the size of the individualentangled bodies in an adsorbent pad formed from the entangled bodiesneed not be uniform and can vary considerably. Generally if knops areproduced by knop producing machines such as that described in U.S. Pat.No. 4,761,857, they will tend to be of a substantially uniform size.Uniformity of size may be of value to yield a predetermined adsorbencycharacteristic to a particular pad consisting of a large number of knopspackaged together.

The major use for an adsorbent material will be where crude oil or otheroil spillages occur on water. The oil tends to float on the surface ofthe water and hence the adsorbent material needs to operate in thisenvironment. The invention envisages shaping a mass of the small bodiesof fibres into a form suitable to adsorb oil masses floating on thesurface of water. The conglomerate of bodies of fibres can thus beshaped into any suitable elongate structure or containment device suchas that described in UK patent specification no. 1266366 which is of alength required to surround the oil spillage and enable the adsorbentmaterial to contact the oil. Thus the mass or conglomerate of bodies ofthe fibres will be contained in a suitable porous enclosure designed toretain the bodies of material in place but permit the liquid such as theoil spillage to contact the adsorbent bodies and to be adsorbed thereby.The outside material can be suitable netting fabric or other porousmaterial.

The whole elongate structure or device must float on the surface of thewater. Wool as well as some synthetic polymers and natural polymers,tend to be more dense than water and hence will not inherently float.Thus the structure may incorporate flotation aids or alternatively thebodies of fibres can be treated or else be processed in such a way thatthey are inherently buoyant on water.

Thus the invention may envisage incorporating substances which arelighter than water into the bodies of fibres to a sufficient degree thatthe bodies are buoyant. Other methods of decreasing the wettability ofthe fibres have been used to increase buoyancy. By doing this the bodiesof fibres are supported by the surface tension of the water and floatrather than being wet out and sinking. For example, small quantities ofoil or similar compounds can be added to increase the floating abilityof the sorbent. It has been found however by adding oil in this way, theabsorbency of the ulitmate bodies of fibres is not essentially reduced.

It has also been found that using the preferred materials, namely knopsof wool fibre, if the wool has been semi-scoured, it leaves residues oforganic materials still on the fibres such as lanolin and wool grease,which provide adequate floatation characteristics to the bodies of woolfibres.

The invention also envisages recovering the oil or other liquid from theadsorbent material for use as may be desired.

This also enables the adsorbent material to be reused again. This reuseis also a feature of the invention.

The invention also envisages providing individually shaped articles orbodies of fibre which are adsorbent for organic substances in a formenabling the shaped material to be transported to a position where itcan perform its function. It is envisaged that these "articles" could beformed of a size small enough to be manually handled, e.g., for simplehousehold functions to sizes for use for example in engineeringworkshops around heavy machines such as lathes where machine oilspillage is very common through larger sizes for trans-shipment on landto situations where spillages might occur of large bulk storage organicmaterial.

In laboratory trials, the following approximate adsorbencies have beenfound for various different types of oil and products of this inventionin comparison to the commercial product "OILSORB".

In order to assess the adsorbency of the wool knops for oil, three quitedifferent grades of oil were acquired. These were chosen to represent awide range of oil viscosities and densities. Firstly crude oil, one ofthe major oil spill contaminants, varies greatly in consistencydepending on where it is source.

Secondly, crude from Newfoundland is waxy and almost solid, whereascrude from South Africa has a similar consistency to diesel.

The biggest proportion of crude is believed to be relatively viscous andresembles heavy fuel oil in viscosity and density. In commercialshipping practice larger quantities of crude oil are shipped thanrefined oil. The following oils were chosen for testing:

    ______________________________________                                        1.    Heavy Fuel Oil                                                                              Density 0.9535 gm/ml                                                          Viscosity = 150 C.S.T. at 50°                      2.    Light Fuel Oil                                                                              Density 0.9107 gm/mk                                                          Viscosity = 34 C.S.T. at 50°                       3.    Gas Oil       Density 0.8233 gm/ml                                                          Viscosity = 3 C.S.T. at 40°                        ______________________________________                                         C.S.T. = Centistokes                                                     

    Weight of Oil adsorbed in comparison                                                    to the weight of Product (Product                                             Weight = 1 unit)                                                                          Light Fuel Heavy Fuel                                   Product     Gas Oil   Oil        Oil                                          ______________________________________                                        Knops (Untreated)                                                                         13        26         35                                           Knops (Oil added)                                                                         10        19         27                                           3M "OILSORB"                                                                              11        11          9                                           ______________________________________                                    

Total adsorbency is one measure of the benefit of an adsorbent material.Another measure is the speed of adsorbency. Again, small scalelaboratory trails have indicated that knops which have not been treatedfor buoyancy, can be fully saturated in 2 to 3 minutes whereas thecommercial product "OILSORE" takes more than 10 minutes.

A number of 5 liter beakers were half filled with tap water and to each500 mls of each of the three test oils were poured on top. To eachbeaker 10 gms of each of the various adsorbency materials was added. Themixture was lightly agitated with a glass stirring rod for 30 seconds.

The adsorbency material was then collected and weighed.

In order to assess the various degrees of adsorbancy of differentmaterials relative to each other, a large water tank 1.0 m×1.3 m wasfilled with tap water to a depth of 0.25 m.

Samples of 3M "OILSORB" in both sheet and boom form together with woolknops loose and also in boom form were floated on the surface. To thistank 500 mls of Heavy Fuel Oil was added and dispersed evenly over thesurface. The samples were left without stirring for 24 hours.

To gain information on how long it takes for each adsorbency product tofully saturate, approximately 30 gm sample of knops and sorbent werefloated on a Heavy Fuel Oil surface. The time taken for the oil topenetrate through the product was recorded.

Small booms approximately 5 cm in diameter were made of wool knops and3M sorbent sheeting. The booms were encased with woven polypropyleneshade cloth. Each was saturated in Heavy Fuel Oil, weighted, then rungthrough rubber squeeze rolls and then reweighted.

The rubber squeeze rolls were 49 cm long and had a pneumatic pressure of3.8 tons applied to them.

Table 1 shows the multiples of each products own weight that wasadsorbed when immersed in various grade of oil.

                  TABLE 1                                                         ______________________________________                                                  Heavy Fuel                                                                              Light Fuel                                                          Oil       Oil        Gas Oil                                        ______________________________________                                        3M Sorbent  × 24.0                                                                              × 21.5                                                                             × 14.6                               Particulate Form                                                              3M Sorbent  × 9.0 × 11.4                                                                             × 10.8                               Sheet Form                                                                    Wool Knops  × 35.0                                                                              × 25.6                                                                             × 13.3                               ______________________________________                                    

From these results it can be seen that the Wool Knops consistentlyadsorbed more oil with the exception of gas oil than the 3M products.

There is a trend that as the viscosity increases the wool knops arecapable of adsorbing more oil.

This is thought to be proportional to the densities of the two sorbentproducts. 3M Sorbent in sheet form has a bulk of 12.5 cc/gm whereas thewool knops have a bulk of 30 cc/gm.

The actual densities of the fibres are, wool 1.1-1.3 gms/ml, andpolypropylene 0.9-0.95 gm/ml. The polypropylene is a highly fibrilatedstructure which gives it a greatly increased surface area. It is thesurface area that normally determines the degree of adsorbency. Thus thespherical shape of the fibres in the knops and the knop itself greatlyaffect the mechanism by which the oil is adsorbed.

The knop has a very porous structure allowing the viscous oils to easilypenetrate the knop. Once the oil is within the knop structure it tendsto be held in by the spherical fibre orientation. If however the oilviscosity is very low, there is a tendency for it to drain out of theknop structure more easily. This does not occur with materials such asair blown polypropylene which works on the principle of having a verylarge surface area to adsorb the oil. Effectively the oil is spread overthe polypropylene fibre surface as a thin film.

To verify this, an additional trial was conducted to ascertain the oilretention capabilities of the various products. Samples were saturatedin Heavy Fuel Oil and left to drain over a metal mesh.

Saturation factors were recorded and again after 2 hours and 20 hours.These are shown in Table II.

                  TABLE II                                                        ______________________________________                                                     Initial 2 Hours  20 Hours                                        ______________________________________                                        3M Sorbent Sheet                                                                             × 14.3                                                                            × 13.0                                                                           × 12.7                                3M Sorbent Chopped                                                                           × 21.5                                                                            × 13.1                                                                           × 11.4                                Wool Knops     × 35.0                                                                            × 15.9                                                                           × 11.2                                ______________________________________                                    

Samples of 3M Sorbent and wool knops both loose and in boom form, weretested for `adsorbency`.

It was found that samples of both wool knops and the 3M products do notgreatly attract oil and absorb it. At the end of the 24 hours soakingtrial, only area of each adsorbency material that were directly incontact with the oil had adsorbed and this amount was minimal.

To increase the potential to adsorb oil it is necessary to have movementof either the sorbent or the oil/water mixture. Using a small wavemaking generator floated in the tank, it was found this helped increasethe adsorbency rate but it was still now spectacular for any of theproducts. To get satisfactory adsorbency there need to be mechanicalagitation either by rotating the booms or allowing them to be agitatedas would occur at a shoreline or with natural wave movement at sea.

In cleaning out the tank between successive trails a handful of looseknops were stirred into the water in the tank and by doing this it waspossible to remove all the floating oil, including the oil sheen, in20-30 seconds.

The times recorded to visually assess how long it took for samples ofloose wool knops and sheet 3M Sorbent were recorded when the sampleswere floated on a Heavy Fuel Oil surface. Knops saturated withoutagitation completely in 2 minutes.

The 3M Sorbent sheet material was not one hundred percent saturatedafter 10 minutes.

A drain trail was devised to determine wools (in wool knop and cardedwool form) ability to retain adsorbed oil. Each adsorbent was immersedin Gas Oil, agitated gently for 45 seconds, removed and the initiallysaturated weight recorded.

The sorbent was then allowed to drain for 1 hour with the retained oilbeing recorded at one minute intervals for 10 minutes then at 5 minutesintervals for 50 minutes.

From these results pick-up factors were calculated.

    ______________________________________                                        Drain Trails - Gas Oil                                                        Density 0.82 gms/ml                                                           Viscosity 3 C.S.T. at 40° C.                                                         SORBENT      SORBENT                                                          WOOLSPILL    CARDED WOOL                                        ______________________________________                                        Total Initial 46.6         33.8                                               Saturated Weight (gram)                                                       ______________________________________                                                Woolspill                                                                     Retained   Pick-up   Carded  Pick-up                                  Time    Wt or Oil  Factor    Wool    Factor                                   (min)   (gram)     of 1 gm   wt of Oil                                                                             of 1 gm                                  ______________________________________                                        1       38.4       12.8      22.5    7.5                                      2       37.7       12.5      21.9    7.3                                      3       37.4       12.4      21.6    7.2                                      4       37.3       12.4      21.5    7.1                                      5       37.1       12.3      21.5    7.1                                      6       37.0       12.3      21.4    7.1                                      7       36.9       12.3      21.3    7.1                                      8       36.9       12.3      21.2    7.0                                      9       36.8       12.2      21.1    7.0                                      10      36.7       12.2      21.1    7.0                                      15      36.4       12.1      20.9    6.9                                      20      36.1       12.0      20.9    6.9                                      25      36.0       12.0      20.9    6.9                                      30      35.8       11.9      20.8    6.9                                      35      35.7       11.9      20.7    6.9                                      40      35.6       11.8      20.6    6.8                                      45      35.5       11.8      20.6    6.8                                      50      35.4       11.8      20.6    6.8                                      55      35.3       11.7      20.6    6.8                                      60      35.2       11.7      20.6    6.8                                      Gram of adsorbed oil                                                                         35.2      20.6                                                 after 60 minutes                                                              ______________________________________                                    

Further comparison trials have been conducted by S. L. RossEnvironmental research Limited of Canada and are reported in a reportentitled "Selection Criteria and Laboratory Evaluation of OilspillSorbents" published by Environment Canada, March 1990. This report andits trial data are incorporated herein by way of reference. This dataconfirms the advantageous properties of the wool knops supplied to RossEnvironmental Research by the applicants for testing as an oil sorbent.

While this invention has been described with reference to preferredembodiments, it is not to be construed as being limited thereto.

We claim:
 1. A method for adsorbing liquid hydrophobic substances whichcomprises the step of contacting the liquid with a plurality ofdiscrete, generally spherical knops of entangled fibrous adsorbentmaterial which have been manufactured by machinery for the production oflong tailed neps.
 2. A method as claimed in claim 1 wherein the materialis in a loose, uncontained form.
 3. A method as claimed in claim 1wherein the knops have a range of densities in order to allow optimisedoil adsorbency for a range of oil viscosities.
 4. A method as claimed inclaim 1 including the step of modifying the fibrous material withchemicals to modify the surface characteristics of the fibers andenhance oil pick-up or buoyancy of the knops in water.
 5. A method asclaimed in claim 4 wherein the chemicals are water repellents.
 6. Amethod as claimed in claim 1 wherein the fibrous material is used inconjunction with a material shaped into an elongated system whichmaterial allows oil and oil water mixtures to penetrate thereby allowingthe knops to absorb the oil.
 7. A method as claimed in claim 6 whereinthe material is a porous housing or netting.
 8. A method as claimed inclaim 1 wherein the fibrous material is used in conjunction with otherfibers or buoyancy aids to increase the oil adsorbancy or buoyancy ofthe knops in water.
 9. A method as claimed in claim 1 wherein thefibrous material is used in conjunction with bacterial nutrients toallow bacteria to break down the oil.
 10. A method as claimed in claim 1wherein the fibrous material is used as a filter, to filter oil from anoil and water mixture.
 11. A method a claimed in claim 1 wherein thefibrous material is used in conjunction with reused, dyed or undyedfibrous materials in knop form.
 12. A method as claimed in claim 1wherein the fibrous material is wool.
 13. A method of separating liquidhydrophobic substances floating on water from the water which comprisesthe steps of:(a) providing a plurality of discrete, generally sphericalknops of entangled fibrous adsorbent material which are floatable onwater, (b) placing said knops of step (a) in contact with said liquidhydrophobic substances such that said liquid hydrophobic substancesbecome adsorbed on said knops, and (c) removing said knops with liquidhydrophobic substances adsorbed thereon from contact with said water.14. A method according to claim 13, including between steps (a) and (b)the step of placing said knops within a plurality of porous containmentmeans.